KR101169162B1 - Coherent single antenna interference cancellation for gsm/gprs/edge - Google Patents

Abstract

A method for midamble estimation includes receiving a burst of symbols, selecting a subset of the burst of symbols comprising a first midamble symbol, for each symbol in the subset, corresponding Calculating a midamble estimation error, and determining a lowest calculated midamble estimation error to locate the first midamble symbol. The receiver is configured to receive a burst of symbols, a timing estimator configured to select a subset of the burst of symbols including a first midamble symbol, a corresponding midamble estimation error for each symbol in the subset. And a processor configured to select a symbol in the subset corresponding to the lowest calculated midamble estimation error as the first midamble symbol.

Description

COHERENT SINGLE ANTENNA INTERFERENCE CANCELLATION FOR GSM / GPRS / EDGE} for GSM / GPRS / EDGE

TECHNICAL FIELD The present invention relates to wireless communications, and in particular, to coherent single antenna interference cancellation.

In many communication systems using GSM, GPRS, EDGE, and the like, the receiver's ability to properly decode the received signal depends on the receiver's ability to maintain accurate symbol timing. However, as wireless communications become much more general, an increase in the amount of interference can adversely affect the receiver's ability to maintain this timing.

In one way of maintaining symbol timing, training sequences (eg, midambles) are known to both transmitters and receivers. The receiver positions the training sequence within a burst of symbols, and thus determines when the data portion of the burst of symbols starts and ends. Positioning a training sequence in an environment with interfering signals can be challenging because the training sequence can be easily overwhelmed by interference from adjacent channels, multipaths, and the like. Accordingly, it would be desirable to provide a receiver capable of reliably positioning a training sequence in a burst of symbols in the presence of interference.

According to one aspect of the invention, a method for midamble estimation includes receiving a burst of symbols, selecting a subset of the burst of symbols comprising a first midamble symbol, within the subset For each symbol, calculating a corresponding midamble estimation error, and determining the lowest calculated midamble estimation error to locate the first midamble symbol.

According to another aspect of the present invention, a method for midamble estimation includes receiving a burst of symbols, selecting a subset of the burst of symbols comprising a first midamble symbol, each within the subset. Determining an estimated channel corresponding to the symbol, suppressing interference on each estimated channel using single antenna interference cancellation, decoding each estimated channel to obtain a corresponding sequence of estimated data symbols Performing a cyclic redundancy check on each sequence of estimated data symbols until a valid condition is detected, and determining that a symbol in the subset corresponding to the valid condition is the first midamble symbol Steps.

According to another aspect of the invention, a receiver is an antenna configured to receive a burst of symbols, a timing estimator configured to select a subset of the burst of symbols comprising a first midamble symbol, each of the subsets For a symbol, a midamble estimator configured to calculate a corresponding midamble estimation error, and a processor configured to select a symbol in the subset corresponding to the lowest calculated midamble estimation error as the first midamble symbol. Include.

According to another aspect of the invention, a receiver is an antenna configured to receive a burst of symbols, a timing estimator configured to select a subset of the burst of symbols comprising a first midamble symbol, each in the subset A channel estimator configured to determine an estimated channel corresponding to the symbol, a single antenna interference cancellation device configured to suppress interference on each estimated channel, each estimated channel to obtain a corresponding sequence of estimated data symbols And a cyclic redundancy check for each sequence of estimated data symbols until a valid condition is detected, wherein the symbols in the subset corresponding to the valid condition are stored in the first midamble. Validation device configured to determine to be a symbol .

According to another aspect of the present invention, the machine-readable medium includes instructions for midamble estimation. The instructions receive a burst of symbols, select a subset of the burst of symbols that includes a first midamble symbol, calculate a corresponding midamble estimation error for each symbol within the subset, and Code for determining the lowest calculated midamble estimation error to locate the first midamble symbol.

According to another aspect of the present invention, the machine-readable medium includes instructions for midamble estimation. The instructions receive a burst of symbols, select a subset of the burst of symbols comprising a first midamble symbol, determine an estimated channel corresponding to each symbol in the subset, and single antenna interference Use cancellation to suppress interference on each estimated channel, decode each estimated channel to obtain a corresponding sequence of estimated data symbols, and determine each of the estimated data symbols until a valid condition is detected. Code for performing a cyclic redundancy check on a sequence and determining that a symbol in the subset corresponding to the valid condition is the first midamble symbol.

It is understood that other configurations of the invention will become apparent to those skilled in the art from the following detailed description, and various configurations of the invention are shown and described by way of example. As will be realized, the invention is capable of other and different configurations and its several details are capable of modification within various other aspects, all of which do not depart from the scope of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

1 illustrates exemplary frame and burst formats in GSM in accordance with an aspect of the present invention.
2 illustrates a receiver for use in a wireless communication system in accordance with an aspect of the present invention.
3 illustrates a subset of symbols, selected by a receiver in accordance with an aspect of the present invention, including a first midamble symbol.
4 illustrates in greater detail a portion of a receiver for use in a wireless communication system in accordance with an aspect of the present invention.
5 illustrates a receiver for use in a wireless communication system in accordance with an aspect of the present invention.
6 illustrates in greater detail a portion of a receiver for use in a wireless communication system in accordance with an aspect of the present invention.
7 illustrates a method for midamble estimation in accordance with an aspect of the present invention.
8 illustrates a method for midamble estimation in accordance with an aspect of the present invention.
9 is a chart illustrating performance improvements achievable using various aspects of the present invention.
10 is a chart illustrating performance improvements achievable using various aspects of the present invention.
11 illustrates a receiver for use in a wireless communication system in accordance with an aspect of the present invention.
12 illustrates a receiver for use in a wireless communication system in accordance with an aspect of the present invention.
13 is a block diagram illustrating a computer system that can implement certain aspects of the present invention.

1 illustrates exemplary frame and burst formats in GSM. The timeline for downlink transmission is divided into multiframes. For the traffic channels used to transmit user-specific data, each multiframe, eg, exemplary multiframe 101, contains 26 TDMA frames labeled TDMA frames 0-25. As identified by the letter “T” in FIG. 1, traffic channels are transmitted in TDMA frames 0-11 and TDMA frames 13-24 of each multiframe. The control channel, identified by the letter "C", is transmitted in the TDMA frame 12. No data is transmitted in the idle TDMA frame 25 (identified by the letter "I") used by the wireless devices to perform measurements for neighbor base stations.

Each TDMA frame, e.g., an exemplary TDMA frame 102, is further divided into eight time slots labeled with time slots 0-7. Each active wireless device / user is assigned one time slot index during the duration for the call. User-specific data for each wireless device is transmitted in the time slots assigned to the wireless device and in the TDMA frames used for the traffic channels.

Transmissions within each time slot are referred to as "bursts" in GSM. Each burst, for example the exemplary burst 103, includes two tail fields, two data fields, a training sequence (or midamble) field, and a guard period GP. The number of bits in each field is shown in parentheses. GSM defines eight different training sequences that can be transmitted in the training sequence field. Each training sequence, eg, midamble 104, is defined to include 26 bits, with the first 5 bits being repeated and the second 5 bits being also repeated. Each training sequence also has a correlation between that sequence and the 16-bit truncated version of the sequence: (a) 16, (b) ± 1, ± 2, ± 3, ± 4, and Zero for a time shift of ± 5, and (3) equal to zero or non-zero value for all other time shifts.

One way of positioning the midamble in series within a burst of symbols is to construct hypotheses about the midamble position to determine which hypothesis provides the highest correlation energy between the known midamble sequence and the hypothesis within the burst of symbols. Compare. This method can be very sensitive to interference from multi-paths of the same midamble sequence, which can cause the correlation energy of incorrect hypotheses to be affected by their time-delayed copies.

2 illustrates a receiver for use in a wireless communication system in accordance with an aspect of the present invention. Receiver 200 includes an antenna 210 configured to receive a wireless signal. Although receiver 200 may be used in a variety of communication systems, for clarity, receiver 200 is specifically described herein for a GSM system. The received signal is provided to a pre-processor 220 that demodulates the signal to produce received samples. Pre-processor 220 may include a GMSK-to-BPSK rotator that performs phase rotation on the received samples. Timing estimator 230 establishes some hypotheses about where the training sequence of symbols (ie, the midamble) starts at the burst of data to receive samples from pre-processor 220 and provide some hypothetical channel estimates. . Interference suppressor 240 performs a single antenna hypothesis cancellation on each of the hypothesized channels, and midamble estimator 250 generates a midamble estimation error for each hypothesis. Timing determination circuit 260 compares the midamble estimation errors for each hypothesis and selects the hypothesis with the lowest midamble estimation error. The selection of the hypothesis of timing determination circuit 260 indicates the position in the burst of symbols at which the midamble is supposed to start. The data processor 270 then processes the received symbols based on this estimated timing and outputs data corresponding to the received symbols.

Rather than using the determined correlation energy to select which midamble timing hypothesis is correct, timing estimator 230 performs a single antenna interference cancellation (“SAIC”) to provide an estimate of the symbols that make up the training sequence. The symbols are compared with previously known symbols of the training sequence to determine an estimation error for it. The operation of timing estimator 230 is illustrated in more detail below.

To begin searching for the first midamble symbol, timing estimator 230 opens a "window" near the estimated start of the midamble sequence. The location of the first symbol of the midamble sequence may be estimated for a given burst, based on the known structure of each burst. For example, as illustrated in FIG. 1, the start of the midamble 104 within the burst 103 begins at the 62nd bit of the burst. Based on this known structure, the timing estimator 230 selects a window 105 of bits representing a series of hypotheses as to where the first midamble symbol may be located. Exemplary window 105 is illustrated in more detail in FIG. 3.

에 대응하고, 심볼 Δ=l은 채널 추정치

에 대응하는 등의 식이다. 도 4에 대해 아래에 더 상세하게 보여지는 바와 같이, 이들 채널 추정치들 각각은 이후 그것에 대한 미드앰블 추정 에러를 결정하기 위해, 그에 대응하는 추정된 미드앰블 심볼들을 결정하도록 간섭 억제기(240) 및 미드앰블 추정기(250)에 의해 프로세싱된다.As can be seen with reference to FIG. 3, the exemplary window 105 includes eleven symbols labeled Δ = 0 to Δ = 10. Each Δ value represents the position of a symbol within the window. However, referring to the position of the symbol within the entire burst, the Δ value is offset by an offset value (eg, Δ = 5 may be offset by 61 to indicate the position of this symbol in the entire burst). For the first seven symbols in window 105, timing estimator 230 generates a channel estimate from the sequence of five adjacent symbols (indicative of the 5-tap channel format of the GSM). For example, the symbol Δ = 0 is a channel estimate

Corresponding to the symbol Δ = l is a channel estimate

To correspond to the equation. As shown in more detail below with respect to FIG. 4, each of these channel estimates is then subjected to an interference suppressor 240 to determine corresponding estimated midamble symbols to determine a midamble estimation error for it. It is processed by the midamble estimator 250.

In the present exemplary aspect, the window 105 is illustrated as consisting of exactly eleven symbols, but the scope of the present invention is not limited to this arrangement. Rather, as will be apparent to those skilled in the art, any window size (up to the size of the maximum total data burst) can be selected. For example, in accordance with one aspect of the present invention, the size of the search window may be selected to be twice the size of the expected minimum propagation delay. Alternatively, the search window size may be parameterized based on any other metric known to those skilled in the art.

는 (가설이 수립된 지연에 대응하는) 수신된 샘플들을 각각의 가설에 대한 레퍼런스 샘플들(즉, 알려진 미드앰블 시퀀스)과 상관시킴으로써 타이밍 추정기(230)에 의해 생성된다. 수신된 신호 y와 가설이 수립된 지연 Δ에 대한 미드앰블 시퀀스 s 간의 상관

에 기초하여, 채널 추정치는 다음과 같이 계산될 수 있다:According to one aspect, the channel estimate

Is generated by timing estimator 230 by correlating the received samples (corresponding to the hypothesized delay) with reference samples for each hypothesis (ie, known midamble sequence). Correlation between received signal y and midamble sequence s for hypothesized delay Δ

Based on this, the channel estimate can be calculated as follows:

To test the hypothesis corresponding to each channel estimate, interference suppressor 240 performs SAIC for each estimated channel. SAIC is a method where oversampled and / or real / imaginary decomposition of a signal is used to provide individual sample sequences to virtual antennas, so that the weights are directed to the beam in the orientation of the desired transmitter and to the orientation of the unwanted interference source. It can be applied to virtual antennas to form a beam null. In general, SAIC can be achieved through one or multiple real antennas at the receiver by using space-time processing, where "space" can be achieved virtually through in-phase and orthogonal components, where "time" is This can be accomplished using late and early samples.

로 대체된다:After SAIC, the previously obtained channel estimate is a time-space channel matrix for one of the subsequent rows, each row representing one of the virtual antennas.

Is replaced by:

The corresponding received samples for the channel estimate are tuned to the time of the hypothesis (assuming to include the midamble), and the corresponding weights of the interference suppression filter are determined:

here,

열벡터이다.For the kth hypothesis

It is a column vector.

은 이후

를 생성하기 위해, 간섭 억제된 샘플들을 사용하여 재추정되며,Channel matrix

Since

Re-estimated using interference suppressed samples, to produce

는 미드앰블 시퀀스 행렬의 의사역(pseudoinverse)이다:here,

Is the pseudoinverse of the midamble sequence matrix:

이며, 여기서

는 채널 행렬을 나타내고,

는 미드앰블 시퀀스의 추정치를 나타낸다. 미드앰블 추정기(250)는 간섭 억제기(240)의 출력을 수신하고, (예를 들어,

,

의 의사역을 통해)

항목을 삭제하며, 따라서, 추정된 미드앰블 시퀀스

는 이전에 알려진 미드앰블 시퀀스

와 비교될 수 있다. 각각의 시간

에 대한 미드앰블 추정 에러

를 획득하기 위해 추정된 미드앰블 시퀀스와 알려진 미드앰블 시퀀스 간의 차이는 수식(9)에 따라 아래에서 결정된다:The output of the interference suppressor 240 is shaped

, Where

Represents the channel matrix,

Denotes an estimate of the midamble sequence. Midamble estimator 250 receives the output of interference suppressor 240 and (eg,

,

Through the doctor's role)

Deletes the item, thus the estimated midamble sequence

Previously known midamble sequence

Can be compared with Each hour

Midamble estimation error for

The difference between the estimated midamble sequence and the known midamble sequence to obtain is determined according to equation (9) below:

은 가설이 수립된 위치

더하기 버스트의 시작으로부터의 오프셋

와 같다:Each hour

Where hypotheses are established

Offset from start of plus burst

Same as:

를 생성한다. 본 발명의 다양한 양상들에 따라, 각각의 채널 추정의 간섭 억제 및 미드앰블 추정은 직렬로, 병렬로, 또는 직렬 및 병렬 프로세싱의 일부 결합을 통해 이루어질 수 있다.4 diagrammatically illustrates the aforementioned calculations occurring in the interference suppressor 240 and the midamble estimator 250, in accordance with an aspect of the present invention. Interference suppressor 240 performs interference cancellation on the channel estimates and reestimates the channel matrix using the interference suppressed samples. Midamble estimator 250 compares the estimated midamble with a known midamble sequence for each hypothesis and provides a midamble estimation error.

. In accordance with various aspects of the present invention, interference suppression and midamble estimation of each channel estimate may be made in series, in parallel, or through some combination of serial and parallel processing.

에 대한 미드앰블 추정

이 결정되면, 타이밍 결정 블록(260)은 어느 가설이 가장 낮은 추정 에러

에 대응하는지를 결정한다. 다른 가설이 수립된 타이밍 값들은 폐기되며, 상기 신호는 결정된 타이밍에 기초하여, 신호 내의 데이터를 디코딩하고 출력하기 위한 데이터 프로세서(270)로 전달된다.Each hour

Midamble Estimation for

Once determined, timing decision block 260 determines which hypothesis has the lowest estimated error.

Determine if it corresponds to. Other hypothesized established timing values are discarded and the signal is passed to a data processor 270 for decoding and outputting data in the signal based on the determined timing.

In accordance with one aspect of the present invention, data processor 270 includes a soft output generator that receives a signal from timing determination block 260 and generates soft decisions that indicate confidence in the detected bits. The soft output generator may implement an Ono algorithm as known in the art. The data processor 270 may further include a de-interleaver to deinterleave the soft decisions, and pass the soft decisions to a Viterbi decoder that decodes the deinterleaved soft decisions and outputs the decoded data.

According to another aspect of the invention, the metric used to determine which midamble timing hypothesis is correct may be a cyclic redundancy check performed after each hypothesis is decoded. For example, FIG. 5 illustrates a receiver 500 in accordance with an aspect of the present invention in which a timing decision is delayed until after a signal corresponding to each hypothesis is decoded.

Receiver 500 includes an antenna 510 configured to receive a wireless signal, such as, for example, an RF modulated GSM signal. The received signal is provided to a pre-processor 520 that demodulates the signal to produce received samples. Pre-processor 520 may also include a GMSK-to-BPSK rotator that performs phase rotation on the received samples. Timing estimator 530 receives some samples from pre-processor 520 and establishes some hypotheses as to where the midamble begins in the burst of data to provide some hypothetical channel estimates. The interference suppressor 540 performs a single antenna interference cancellation on each of the hypothesized channels, and the data processor 550 then processes the received symbols for each hypothesized channel and receives the received symbols. Outputs data corresponding to Cyclic redundancy check (“CRC”) 560 is performed on the data output for each hypothesized channel and continues until one of the data streams is verified. The timing decision block 570 then selects a hypothesis corresponding to the validation condition and discards other hypotheses.

내지

를 수신하고, 각각의 채널 추정치에 대해 SAIC 및 최대 우도 시퀀스 추정("MLSE") 등화 모두를 수행한다. 간섭 억제기(540)는 이후 데이터 프로세서에 대한 각각의 가설에 대응하는 필터링된 신호들을 제공한다. 데이터 프로세서(550)는 간섭 억제기(540)로부터 필터링된 신호들을 수신하고 검출된 비트에서 신뢰도를 표시하는 소프트 결정들을 생성하는 복수의 소프트 출력 생성기들을 포함한다. 데이터 프로세서(550)는, 소프트 결정들을 디인터리빙하고, 디인터리빙된 소프트 결정들을 디코딩하는 복수의 비터비 디코더들로 상기 소프트 결정들을 전달하고, CRC 블록(560)으로 디코딩된 데이터를 출력하는, 복수의 디-인터리버들을 더 포함한다.6 illustrates the operation of interference suppressor 540 and data processor 550 in more detail, in accordance with an aspect of the present invention. Interference suppressor 540 takes channel estimates from timing estimator 530.

To

And perform both SAIC and maximum likelihood sequence estimation ("MLSE") equalization for each channel estimate. Interference suppressor 540 then provides filtered signals corresponding to each hypothesis for the data processor. The data processor 550 includes a plurality of soft output generators that receive the filtered signals from the interference suppressor 540 and generate soft decisions that indicate reliability in the detected bits. The data processor 550 demultiplexes the soft decisions, passes the soft decisions to a plurality of Viterbi decoders that decode the deinterleaved soft decisions, and outputs the decoded data to the CRC block 560. Further includes de-interleavers.

Although the example aspects described above are illustrated as performing parallel interference suppression and decoding on each estimated channel, the scope of the present invention is not limited to this arrangement. Rather, a single interference suppressor and a single data processor can be used to process each estimated channel in a serial manner. Alternatively, the receiver can use a combination of serial and parallel processing (eg, via a suppressor of interferences and two channels per data processor, etc.).

7 is a flow diagram illustrating a method for midamble estimation in accordance with an aspect of the present invention. The method begins with step 701, in which the receiver receives a burst of symbols. In step 702, the receiver selects a subset of the burst of symbols that includes the first midamble symbol. In step 703, the receiver determines an estimated channel corresponding to each symbol in the selected subset. In step 704, the receiver performs SAIC on each estimated channel to obtain an estimated midamble sequence. In step 705, the receiver compares each estimated midamble sequence with a previously known midamble sequence to determine a midamble estimation error corresponding to each estimated channel. In step 706, the receiver determines which estimated channel corresponds to the lowest midamble evaluation error to locate the first midamble symbol. In step 707, based on the determined position of the first midamble symbol, the data sequence within the burst of symbols is decoded.

8 is a flow diagram illustrating a method for midamble estimation in accordance with an aspect of the present invention. The method begins at step 801 where a receiver receives a burst of symbols. In step 802, the receiver selects a subset of the burst of symbols that includes the first midamble symbol. In step 803, the receiver determines an estimated channel corresponding to each symbol in the selected subset. In step 804, the receiver performs SAIC on each estimated channel, and each estimated channel is decoded to obtain a corresponding sequence of estimated data symbols. In step 806, the receiver performs a cyclic redundancy check ("CRC") on the estimated data symbols for each estimated channel until a valid condition is found. In step 807, the receiver determines that the symbols in the selected subset in step 802 corresponding to valid conditions are the first midamble symbols.

9 is a chart illustrating performance improvements achievable using various aspects of the present invention. 9 charts the frame error rate over a range of carrier to interference (“C / I”) levels for example receiver systems using the midamble estimation techniques described in more detail above. As can be seen with reference to FIG. 9, the performance of the receiver system 900 for estimating midamble timing using correlation energy is less than optimal because four timing hypotheses provide an improved frame error rate. This is because (Δ = 3, Δ = 4, Δ = 5 & Δ = 6). In particular, as the amount of interference increases, a receiver system that estimates midamble timing using midamble estimation error or CRC validity is more likely to select one of these preferred timings than receiver system 900. This improved performance is illustrated in more detail in FIG. 10 with the probability that an exemplary receiver system using midamble estimation error will select a given midamble timing. As can be seen with reference to FIG. 10, the receiver system 900 (which estimates the midamble timing using the correlation energy) is better than the receiver system 1002 that estimates the midamble timing using the midamble estimation error. The larger frequency is used to select the lane's midamble symbol timing values (eg, Δ = 0, Δ = l, Δ = 2). Indeed, the receiver system 1002 selects either Δ = 5 and Δ = 6 for more than 80% of the time. As can be seen with reference to FIG. 9, these timings enjoy approximately 6 dB better performance than the average performance of the receiver system 900. Even better performance benefits can be achieved through a receiver system that selects a midamble based on the CRC of the decoded data, but correspondingly increases in processing complexity.

11 illustrates a receiver for use in a wireless communication system in accordance with an aspect of the present invention. Receiver 1100 includes an antenna module 1110 configured to receive a wireless signal, such as, for example, an RF modulated GSM signal. The received signal is provided to a pre-processing module 1120 that demodulates the signal to produce received samples. The pre-processing module 1120 may also include a GMSK-to-BPSK rotator that performs phase rotation on the received samples. Timing estimation module 1130 receives samples from pre-processing module 1120 and provides some hypotheses about where the training sequence (midamble) of symbols begins in the burst of data to provide some hypothetical channel estimates. Establish. The interference suppression module 1140 performs a single antenna interference cancellation on each of the hypothesized channels, and the midamble estimation module 1150 generates a midamble estimation error for each hypothesis. Timing determination module 1160 compares the midamble estimation errors for each hypothesis and selects the hypothesis with the lowest midamble estimation error. The selection of the hypothesis by timing determination module 1160 indicates a location within a burst of symbols for which the midamble is supposed to start. The data processing module 1170 then processes the received symbols based on this estimated timing and outputs data corresponding to the received symbols.

12 illustrates a receiver 1200 for use in a wireless communication system in accordance with an aspect of the present invention. Receiver 1200 includes an antenna module 1210 configured to receive a wireless signal, such as, for example, an RF modulated GSM signal. The received signal is provided to a pre-processing module 1220 that demodulates the signal to produce received samples. Pre-processing module 1220 may also include a GMSK-to-BPSK rotator that performs phase rotation on the received samples. Timing estimation module 1230 receives samples from pre-processing module 1220 and provides some hypotheses about where the training sequence (midamble) of symbols begins in the burst of data to provide some hypothetical channel estimates. Establish. The interference suppression module 1240 performs a single antenna interference cancellation on each of the hypothesized channels, and then the data processing module 1250 processes the received symbols for each hypothesized channel and receives the received symbols. Outputs data corresponding to Cyclic redundancy check (“CRC”) is performed in module 1260 on the data output for each hypothesized channel and continues until one of the data streams is identified. The timing determination module 1270 then selects a hypothesis corresponding to the confirmation condition and discards other hypotheses.

13 is a block diagram illustrating a computer system 1300 that can implement an aspect. Computer system 1300 includes a bus 1302 or other communication mechanism for conveying information, and a processor 1304 coupled with a bus 1302 for processing information. Computer system 1300 may also include a memory 1306, such as random access memory (“RAM”) or other dynamic storage device, coupled to bus 1302 for storing instructions and information to be executed by processor 1304. It includes. Memory 1306 may also be used to store time varying information or other intermediate information during execution of instructions to be executed by processor 1304. Computer system 1300 further includes a data storage device 1310, eg, a magnetic disk or an optical disk, coupled to bus 1302 to store information and instructions.

Computer system 1300 may be coupled via I / O module 1308 to a display device (not shown), such as a cathode ray tube (“CRT”) or liquid crystal display (“LCD”) for displaying information to a computer user. Can be. For example, an input device, such as a keyboard or mouse, may also be coupled to the computer system 1300 via an I / O module 1308 for conveying information and command selections to the processor 1304.

According to one aspect, midamble estimation is performed by computer system 1300 in response to processor 1304 executing one or more sequences of one or more instructions contained in memory 1306. Such instructions may be read into memory 1306 from another machine-readable medium, such as data storage device 1310. Execution of the sequences of instructions contained in main memory 1306 may cause processor 1304 to perform the process steps described herein. One or more processors in the multi-processing apparatus may also be used to execute the sequences of instructions contained in the memory 1306. In alternative aspects, hard-wired circuitry may be used in place of or in combination with software instructions to implement various aspects. Thus, aspects are not limited to any particular combination of hardware circuitry and software.

The term “machine-readable medium” as used herein refers to any medium that participates in providing instructions to the processor 1304 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as data storage device 1310. Volatile media includes dynamic memory, such as memory 1306. The transmission medium includes coaxial cables, copper wire and optical fibers, including wires comprising bus 1302. The transmission medium may also take the form of acoustic or light waves, such as generated during, for example, radio frequency or infrared data communication. Common forms of machine-readable media include, for example, floppy disks, flexible disks, hard disks, magnetic tapes, any other magnetic media, CD-ROMs, DVDs, any other optical media, punched cards, paper tapes. , Any other physical medium having patterns of holes, RAM, PROM, EPROM, FLASH EPROM, any other memory chip or cartridge, carrier, or any other medium readable by a computer.

Those skilled in the art will appreciate that various exemplary blocks, modules, elements, components, methods, and algorithms described herein can be implemented as electronic hardware, computer software, or combinations of both. In addition, they may be divided differently from those described above. To illustrate this interchangeability of hardware and software, various illustrative blocks, modules, elements, components, methods, and algorithms have been described generally in terms of their functionality. Whether such functionality is implemented in hardware or software depends on the particular application and design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in a variable manner for each particular application.

The specific order or hierarchy of steps or blocks in the processes disclosed is an illustration of example approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps or blocks in the processes may be rearranged. The accompanying method claims present elements of the various steps in a sample order, and are not intended to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to implement the various aspects described herein. Various modifications to these aspects will be apparent to those skilled in the art, and the generic principles defined herein apply to other aspects. Accordingly, the claims are not intended to be limited to the aspects set forth herein but are to be accorded the full scope of the linguistic claims, and reference to a singular element means "only one" unless specifically stated otherwise. It is not intended to be meant, but to mean "one or more". Unless specifically stated, the term “some” refers to one or more. Male pronouns (eg, his) include females and neutrals (eg, her and its) and vice versa. All structural and functional equivalents to the elements of the various aspects that are known to one of ordinary skill in the art or that will be described later throughout this application are expressly incorporated herein by reference and are intended to be included by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. If the element is a phrase "means for" or a method claim, then no claim element shall be used unless the element is cited using the phrase "step to do". §112, it should not be interpreted under the provisions of paragraph 6.

Claims (38)

A method for midamble estimation, performed by a receiver of a communication device, the method comprising:
Receiving a burst of symbols;
Selecting a subset of the burst of symbols that includes a first midamble symbol;
For each symbol in the subset, calculating a corresponding midamble estimation error; And
Determining the lowest calculated midamble estimation error to locate the first midamble symbol;
Method for midamble estimation. The method of claim 1,
Decoding the burst of symbols to determine a data sequence for the burst of symbols;
Method for midamble estimation. The method of claim 1,
Computing the midamble estimation error for each symbol in the subset,
Determining an estimated channel corresponding to the symbol;
Performing a single antenna interference cancellation on the estimated channel to obtain an estimated midamble sequence; And
Comparing the estimated midamble sequence with a previously known midamble sequence to determine the midamble estimation error;
Method for midamble estimation. The method of claim 3,
Computing the midamble estimation error for each symbol in the subset,
Performing a single antenna interference cancellation on the estimated channel to obtain an estimated data sequence for the burst of symbols; And
Comparing the estimated data sequence with a previously determined data sequence to determine the midamble estimation error,
Method for midamble estimation. The method of claim 3,
Determining an estimated channel corresponding to each symbol includes selecting adjacent symbols in the subset of the predetermined number corresponding to the number of taps in the estimated channel,
Method for midamble estimation. The method of claim 1,
Selecting the subset of burst symbols includes estimating a position of the first midamble symbol within a burst of symbols and selecting a plurality of symbols centered around the estimated position;
Method for midamble estimation. delete delete delete As a receiver,
An antenna configured to receive a burst of symbols;
A timing estimator configured to select a subset of the burst of symbols that includes a first midamble symbol;
A midamble estimator configured to calculate a corresponding midamble estimation error for each symbol in the subset; And
A processor configured to select a symbol in the subset corresponding to the lowest calculated midamble estimation error as the first midamble symbol;
receiving set. The method of claim 10,
Further comprising a decoder configured to decode the burst of symbols to determine a data sequence for the burst of symbols;
receiving set. The method of claim 10,
The midamble estimator,
Determine an estimated channel corresponding to the symbol;
Perform single antenna interference cancellation on the estimated channel to obtain an estimated midamble sequence; And
Calculate the midamble estimation error for each symbol in the subset by comparing the estimated midamble sequence with a previously known midamble sequence to determine the midamble estimation error.
receiving set. The method of claim 12,
The midamble estimator,
Perform a single antenna interference cancellation on the estimated channel to obtain an estimated data sequence for the burst of symbols; And
And further calculate the midamble estimation error for each symbol in the subset by comparing the estimated data sequence with a previously determined data sequence to determine the midamble estimation error.
receiving set. The method of claim 12,
The midamble estimator is configured to determine the estimated channel corresponding to each symbol by selecting adjacent symbols in the subset of the predetermined number corresponding to the number of taps in the estimated channel;
receiving set. The method of claim 10,
The timing estimator is configured to estimate a position of the first midamble symbol within the burst of symbols and to select the subset of burst symbols by selecting a plurality of symbols centered around the estimated position;
receiving set. delete delete delete delete As a receiver,
Means for receiving a burst of symbols;
Means for selecting a subset of the burst of symbols comprising a first midamble symbol;
Means for calculating a corresponding midamble estimation error for each symbol in the subset; And
Means for selecting a symbol in the subset corresponding to the lowest calculated midamble estimation error as the first midamble symbol,
receiving set. 21. The method of claim 20,
Means for decoding the burst of symbols to determine a data sequence for the burst of symbols;
receiving set. 21. The method of claim 20,
Means for calculating a corresponding midamble estimation error for each symbol in the subset,
Determine an estimated channel corresponding to the symbol;
Perform single antenna interference cancellation on the estimated channel to obtain an estimated midamble sequence; And
And compare the estimated sequence with a previously known midamble sequence to determine the midamble estimation error.
receiving set. The method of claim 22,
Means for calculating a corresponding midamble estimation error for each symbol,
Perform a single antenna interference cancellation on the estimated channel to obtain an estimated data sequence for the burst of symbols; And
Further configured to compare the estimated data sequence with a previously determined data sequence to determine the midamble estimation error,
receiving set. The method of claim 22,
Means for calculating the midamble estimation error,
And determine the estimated channel corresponding to each symbol by selecting adjacent symbols in the subset of the predetermined number corresponding to the number of taps in the estimated channel.
receiving set. 21. The method of claim 20,
Means for selecting the subset of burst symbols is configured to estimate a position of the first midamble symbol within the burst of symbols and to select a plurality of symbols centered around the estimated position,
receiving set. delete delete delete delete A computer-readable medium storing computer program instructions for midamble estimation, comprising:
The instructions,
Receive a burst of symbols;
Select a subset of the burst of symbols that includes a first midamble symbol;
Calculate a corresponding midamble estimation error for each symbol in the subset; And
A code for determining a lowest calculated midamble estimation error to locate the first midamble symbol;
Computer-readable media. 31. The method of claim 30,
The instructions,
Further comprising code for decoding the burst of symbols to determine a data sequence for the burst of symbols;
Computer-readable media. 31. The method of claim 30,
Code for calculating the midamble estimation error for each symbol in the subset is:
Determine an estimated channel corresponding to the symbol;
Perform single antenna interference cancellation on the estimated channel to obtain an estimated midamble sequence; And
A code for comparing the estimated midamble sequence with a previously known midamble sequence to determine the midamble estimation error,
Computer-readable media. 33. The method of claim 32,
Code for calculating a corresponding midamble estimation error for each symbol in the subset,
Perform a single antenna interference cancellation on the estimated channel to obtain an estimated data sequence for the burst of symbols; And
Further comprising code for comparing the estimated data sequence with a previously determined data sequence to determine the midamble estimation error;
Computer-readable media. 33. The method of claim 32,
Code for determining an estimated channel corresponding to each symbol comprises code for selecting adjacent symbols in the subset of the predetermined number corresponding to the number of taps in the estimated channel,
Computer-readable media. 31. The method of claim 30,
Code for selecting a subset of the burst symbols includes code for estimating the position of the first midamble symbol within the burst of symbols and selecting a plurality of symbols centered around the estimated position ,
Computer-readable media. delete delete delete

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